Method for preparing polyvinyl chloride

ABSTRACT

Vinyl chloride is suspension polymerized in the presence of a catalyst selected from the group consisting of dialkyl peroxy dicarbonate, azo-bis-2,4-dimethyl valeronitrile, azo-bis-2,4,4trimethyl valero nitrile, azo-bis-4-methoxy-2,4-dimethyl valeronitrile, and acetyl cyclohexyl sulfonyl peroxide, a suspending agent, a fatty alcohol having from eight to 18 carbon atoms and sorbitan oleate. When the rate of conversion reaches at least 50 percent, an organic reducing agent is added to the polymerization system. A polyvinyl chloride having superior particle size distribution, plasticizer absorption, fish eye, initial color and thermal stability is produced.

United States Patent Koyanagi et al.

[451 June 20, 1972 [54] METHOD FOR PREPARING POLYVINYL CHLORIDE I 73Assignec: Shinetsu Chemical Company I22] Filed: March 1, I971 2| Appl.No.: 120,041

[30] Foreign Application Priority Data Sept. 30, 1970 Japan ..45/85120[52] US. Cl. ..260/87.l, 260/78.5 CL, 260/863, 260/875 R, 260/875 C,260/875 G, 260/877,

[5 l Int. Cl. ..C08f 1/11, C08f 3/30, C08f 15/02 [58] Field ofSearch..260/87.5,92.8 W, 87.1

[56] References Cited UNITED STATES PATENTS 2,528,469 10/1950 Condo etal ..260/92.8 W

Abercrombie et al. ..260/92.8 W Beer et al ..260/928 W PrimaryExaminer-Joseph L. Schofer Assislant Examiner-John A. Donahue, Jr.

Anurne vHarry C. Bierman, Jordan B. Bierman and Bierman & Bierman 5 7ABSTRACT Vinyl chloride is suspension polymerized in the presence of acatalyst selected from the group consisting of dialkyl peroxydicarbonate, azo-bis-2,4-dimethyl valeronitrile, azo-bis-2,4,4-trimethyl valero nitrile, azo-bis-4-methoxy-2,4-dimethyl valeronitrile,and acetyl cyclohexyl sulfonyl peroxide, a suspending agent, a fattyalcohol having from eight to 18 carbon atoms and sorbitan oleate. Whenthe rate of conversion reaches at least 50 percent, an organic reducingagent is added to the polymerization system. A polyvinyl chloride havingsuperior particle size distribution, plasticizer absorption, fish eye,initial color and thermal stability is produced 6 Claims, No DrawingsMETHOD FOR PREPARING POLYVINYL CHLORIDE This invention relates to animproved method for producing polyvinyl chloride by the suspensionpolymerization of vinyl chloride or a mixture of vinyl monomerscontaining vinyl chloride as its main component. The suspensionpolymerization of vinyl chloride has hitherto been conducted in thepresence of an oil-soluble catalyst. in the known method a protectivecolloid such as polyvinyl alcohol, cellulose ether, a copolymer ofmaleic anhydride with vinyl acetate or, styrene, gelatin, or starch isused as the suspending agent. The use of a polymerization catalysthaving an extremely high activity, as for example a dialkylperoxydicarbonate such as diisopropyl peroxydicarbonate (lPP), dicyclohexylperoxydicarbonate (DCPP), or azobis-2,4-dimethyl-valeronitrile (DMVN) oracetylcyclohexyl sulfonyl peroxide (ACSP), is also known. It is furtherknown that these high activity catalysts increase the polymerizationreaction rate over the reaction rates afforded by catalysts havingcomparatively low activity as for example lauroyl peroxide andazobisisobutylonitrile. However, high activity catalysts rapidlydecompose in the polymerization system. This makes it very different tocontrol the rate of conversion. Further, it tends to have an adverseeffect on the properties of the polyvinyl chloride (PVC) produced.Consequently, the amount of high activity catalyst employed must bestrictly controlled. The use of only a slight excess of high activitycatalyst will accelerate the reaction rate to such an extent that thereaction will be uncontrollable. This will adversely affect the particlesize distribution and the initial color of the polyvinyl chlorideproduced. Moreover, it will result in a reduction of the porosity of theproduced polyvinyl chloride. The process may have to be'halted, if dueto the uncontrolled reaction, it becomes unsafe. When a peroxydicarbonate, an azo compound having a high activity, or ACSP is used,the polyvinyl chloride which is produced tends to have, for some unknownreason, inferior initial color and thermal stability as compared topolyvinyl chloride produced with the use of a low activity catalyst suchas lauroyl peroxide. This holds true even though the peroxy dicarbonate,high activity azo compound or ACSP employed is not employed in excess.Further, when said peroxy dicarbonate, high activity azo compound orACSP is used, one gets completely unpredictable results with respect tothe particle size distribution, gelling property and adsorption ofplasticizer.

Several proposals have been made to overcome these difficulties-forexample, the joint use of both a high activity catalyst and a lowactivity catalyst and the use of the additives with the high activitycatalyst. However, these unknown methods have disadvantages. Until thepresent invention, there was no method known which could make the bestuse of a high activity catalyst and solve the problems referred toabove.

It is an object of this invention to provide a simple and economicalmethod for producing a superior quality vinyl chloride polymer using theabove-given high activity catalyst. The method of the present inventionis characterized in that vinyl chloride or a mixture of vinyl monomerscontaining vinyl chloride as its main component is suspensionpolymerized in the presence of at least one polymerization catalystselected from the group consisting of dialkylperoxy dicarbonates,azobis-2,4dimethyl valeronitrile, azo-bis-2,4,4-trimethyl valeronitrile,azo-bis-4-methoxy-2,4-dimethyl valeronitrile, and acetylcyclohexylsulfonyl peroxide, a saturated fatty alcohol having eight to 18 carbonatoms, and sorbitan oleate. The polymerization mixture is agitated to.initiate the polymerization. When the rate of conversion reaches atleast 50 percent,- an organic reducing agent is added to thepolymerization reaction mixture.

The method of the present invention will now be described in greaterdetail. The use of a higher fatty alcohol in the suspensionpolymerization of vinyl chloride is well known. it is also known thatthe addition of a higher fatty alcohol to a polymerization system inwhich a dialkylperoxy dicarbonate, such as lPP, is employed as thecatalyst, results in a substantial improvement in initial color andthermal stability of the produced polyvinyl chloride. However, if toomuch dialkylperoxy dicarbonate, high activity azo compound or highactivity ACSP is used, the effectiveness of the added higher fattyalcohol will be suppressed. Thus when the polyvinyl chloride product isto be mixed with a large amount of a plasticizer so as to enable its useas a so-called flexible product, the amount of higher alcohol employedmust be increased considerably. This raises production cost. Thisdifficulty is overcome in the method of the present invention, by addingboth sorbitan oleate and an organic reducing agent to the polymerizationsystem. When the suspension polymerization of vinyl chloride or amixture of vinyl monomers containing vinyl chloride as its maincomponent is conducted in the presence of said higher fatty alcohol,sorbitan oleate and organic reducing agent, an improvement of theinitial color and thermal stability of the polyvinyl chloride producedresults. Moreover, this is coupled with an improvement in the particlesize distribution and porosity of the polyvinyl chloride product. Thusthe method of the present invention results in the production of apolyvinyl chloride having superior processability.

The present invention is based on our finding that sorbitan oleate isthe only additive that enablespolyvinyl chloride, prepared in thepresence of the above mentioned catalysts. to concurrently possesssuperior processability, initial color and thermal stability. It is alsobased on our finding that the sorbitan oleate is most effective whenemployed together with a higher fatty alcohol and an organic reducingagent. It should, however, be noted that the organic reducing agent actsas a polymerization inhibitor. Therefore, it should not be added at anearly stage of the polymerization reaction. instead, it should be addedwhen the rate of conversion has reached at least 50 percent.

The catalyst employed in practicing the method of the instant invention,comprises at least one member selected from the group consisting ofdialkyl peroxydicarbonates (such as diisobutylperoxydicarbonate,diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate,dicyclohexyl peroxydicarbonate and bis-l,4-tertiary butyl cyclohexylperoxydicarbonate azonitriles (such asazo-bis-2,4-dimethylvaleronitrile, azo-bis-Z,4-trimethylvaleronitrileand azo-bis-4-methoxy-2,4- dimethylvaleronitrile), and acetylcyclohexylsulfonyl peroxide. Along with the catalyst one may employ thosematerials which are usually used in the suspension polymerization ofvinyl chloride-for example, lauroyl peroxide, benzoyl peroxide andazobis-isobutyronitirle. The amount of catalyst to be used varies withand is dependent upon the kind of polyvinyl chloride to be prepared, itsintended use, the desired rate of conversion. Preferably the catalyst isemployed at a concentration of at most 0.2 part by weight, morepreferably at most 0.1 part by weight, based on the amount of the vinylchloride monomer or the mixture of vinyl monomers containing vinylchloride monomer.

Any of the known suspending agents usually employed in thepolymerization of vinyl chloride may be used. For example, polyvinylalcohol, partially saponified polyvinyl acetate having a saponificationdegree of at least percent, polyvinylmethyl ether, water-solublecopolymers of polyvinylmethyl ether, copolymers of maleic anhydride withvinyl acetate or styrene, partially saponified polyacrylic esters,cellulose ethers such as methylcellulose, hydroxyethyl methylcellulose,hydroxypropyl methylcellulose ether, carboxymethylcellulose ether,gelatin, starch and gum arabic. The suspending agent is added to thepolymerization system usually in an amount of from 0.01 to 0.5 percentby weight, based on the amount of the vinyl chloride monomer or mixtureof vinyl monomers containing vinyl chloride monomer.

The higher fatty alcohol to be added to the vinyl chloridepolymerization system must be a saturated alcohol having from eight to18 carbon atoms. Examples of said higher fatty alcohol include octylalcohol, decanoyl alcohol, lauryl alcohol, myristyl alcohol, cetylalcohol, and stearyl alcohol. The higher fatty alcohol is employed inthe polymerization inan amount of from 0.03 to 0.1 percent by weightbased on the amount of the vinyl chloride monomer or mixture of vinylmonomers containing vinyl chloride monomer. if it is added in an amountof less than 0.03 percent, the alcohol will not exert a sufficienteffect. The addition of more than 0.1 percent alcohol is uncalled for assuch addition will not afford a propor tional increase in its desiredeffect. The sorbitan oleate used with the higher fatty alcohol isexemplified by sorbitan monooleate, sorbitan trioleate and sorbitansesquioleate. The sorbitan oleate is preferably used in an amount offrom 0.01 to 0.5 percent by weight, based on the weight of the vinylchloride monomer or mixture of vinyl monomers containing vinyl chloridemonomer. If itis used in a amount of less than 0.01 percent by weight,the sorbitan oleate will not have a sufficient effect. If it is used inan amount over 0.5 percent, the rate of reaction will be substantiallydecreased. The reducing agent, which is added to the polymerizationsystem when the rate of conversion reaches at least 50 percent, isselected from the. group consisting of hydroquinone, biphenol A, andsulfoxide prepared from a formaldehyde condensate. The reducing agentmay be added to the suspension after the polymerization is overproviding that the rate of conversion of the system is at least 50percent. The reducing agent is added to the polymerization system in anamount of at least 0.005 percent 'by weight, based on the amount ofvinyl chloride polymer.

Preferably it is added in an amount of from 0.005 to 0.05 percent, basedon the amount of vinyl chloride polymer because, if it is added in anamount more than 0.05 percent, the thermal stability of the vinylchloride polymer produced may be adversely affected.

it should be noted that with respect to each of the catalyst, suspendingagent, fatty alcohol, sorbitan oleate and reducing agent, one can employone representative compound or a mixture of representative compoundsfrom the above given respective groups. Various organic solvents mayalso be used to control the molecular weight of the polyvinyl chloride.

The polymerization of the present invention is preferably carried out ata temperature of from 30 to 70 C, which temperature range is that whichis usually employed in the known methods for the suspensionpolymerization of vinyl chloride.

The method of the present invention can however be effectively carriedout even at temperatures below 30 C. In such case, a special catalystsuch as trialkyl boron or an alcohol such as methanol or ethanol may beconcurrently employed.

The method of the present invention is applicable not only to thepolymerization of vinyl chloride alone, but also to the copolymerizationof vinyl chloride with other vinyl monomers copolymerizable with it.Examples of such vinyl monomers include vinyl esters, vinyl ethers,alkyl acrylates, alkyl methacrylate, maleic anhydride,alkyl esters ofmaleic acid or of fumaric acids, alkyl itaconates, aromatic vinyls,vinylidene halides, vinyl halides excepting vinyl chloride, anda-olefins having at placed in a tube, the bottom of which was filledwith glass fiber to permit removal of DOP. The tube was then placed in acen trifugal separator and was rotated therein at a speed of 3,000 rpm,for a period of 1 hour. The separated DOP was removed, and the PVC whichhad absorbed DOP was weighed. The ratio (in percent) of DOP absorbed by100 g of PVC was derived from the ratio of the weight of PVC before ithas absorbed DOP to that of PVC after it had absorbed DOP.

2. Initial Color Fifty parts of DOP, 1 part of dibutyltin dilaurate and0.5 part of cadmium stearate were added to 100 parts of the polyvinylchloride (PVC) and mixed therewith at 100 C, for 30 minutes. The mixturewas then molded into a 5 X 10 mm angular stick by means of an extruderhaving an inside diameter of 20 mm. The cylinder temperature of theextruder was 160 C. The die temperature was 195 C. The color of thestick as observed with the naked eye was used as a measure of theinitial color of the PVC.

3. Thermal Stability v 2.5 parts of dibutyltin maleate and 0.5 part ofstearic acid were added to 100 parts of PVC. The mixture was kneaded for10 minutes on a hot roll at 170 C to produce a 0.7 mm thick sheet. Thesheet was heated at l C in a gear oven. The time elapsed before thesheet blackened was used as a measure of the thermal stability of thePVC.

4. Fish Eye Fifty parts of DOP, 2.0 parts of dibutyltin dilaurate, 0.8part of cetyl alcohol, 0.] part of barium stearate, 0.] part of cadmiumstearate, 0.5 part of titanium oxide, and 0.1 pan of carbon black wereadded to parts of PVC. The mixture was kneaded for 7 minutes on a hotroll at 150 C to produce a 0.2 mm thick sheet. Light was passed throughthe sheet and the number of fish eyes per 100 cm of the sheet,- asobserved with the naked eye, was employed as an indication of the extentof fish eye production in the PVC.

Controls I ll Five-hundred liters of water were placed into a stainlesssteel polymerizing vessel, having an inner capacity of 1,000 liters.Two-hundred gram of partially saponified polyvinyl acetate(saponification degree: 81 mole percent, average degree ofpolymerization: L820), cetyl alcohol and sorbitan monooleate each in theamount given in Table l, and 250 kg of vinyl chloride monomer weredissolved therein. Upon the further addition of 37.5 g of IN,polymerization was carried out at 57 C for 10 hours. Unreacted vinylchloride monomer was removed from the system. The polymerization productwas stirred for 15 minutes with (or without) an addition of a methanolsolution of biphenol A in the amount given in Table 1. Then thepolymerization product produced was dehydrated and dried. The propertiesof the PVC thus produced are shown in the following Table l.

TABLE 1 Control Number 1 2 3 4 5 6 7 8 9 10 11 12 Amount of cetylalcohol (percent)/VC* 0 0.01 0. 2 1. 5 0 0 0 0. 2 0. 2 0 0. 2 Amount ofsorbitan monooleate (percent)/VC* 0 0 0 0 0 003 0 05 1.0 0 0.0 0 0 050.05 Amount of bisphenol A (percent) /V C" 0 0 0 0 0 0 0 0.02 0 0.02 002 0. 1 Particle size distribution (percent):

60 mesh pass 88.5 89.2 90.3 86.3 .5 .0 97. 8

100 mesh pass 38. 3 40. 5 43. 5 35. 5 .0 .1 49. 9

200 mesh pass 3.6 2. 9 4. 5 4. 0 .3 -9 0 DOP absorption (percent) 17.516.3 16.5 15.9 .9 30.5 Fish oyo (pieces) 110 200 3 30 Initial color 4 44 3 3 1 Thermal stability 111111.) so 90 90 90 0 60 '(lvrcuuU/VC menuspercent based on the weight of the vinyl chloride.

. permitted to stand at room temperature for 1 hour. It was thenExamples l-8 Five-hundred liters of water, 200 grams of partiallysaponified polyvinyl acetate (saponification degree: 81 mole percent;average degree of polymerization: 1,820). cetyl alcohol and sorbitanmonooleate each in the amount given in Table 2, and 250 kg of vinylchloride monomer were charged into a stainless steel polymerizationvessel having an inner capacity of 1,000 liters. 37.5 g of IPP wereadded thereto and polymerization was carried out at 57 C for ID hours.Un-

reacted vinyl chloride monomer was removed from the TABLE 5 system.Brphenol A was added in the amount given in Table 2. Nu Example 13Example 14 The polymerization product was stirred for 15 minutes, thenKind of reducing agent Hydroquinone SFS dehydrated and dried. Theproperties of the PVC thus Initial C0101 l 1 prepared are shown in Table2 below. Thermal Stablmy (mm) 100 TABLE 2 Example Number 1 2 3 4 5 6 7 8Amount 01 cetyl alcohol (percent)/VC* 0. 2 0.2 0.05 0.05 0. 1 0.1 0.5(1. 1 Amount of sorbitan monooleate (pereent)/VC 0.05 0. 1 0.05 0. 1 0.05 0.05 0.2 0. 2 Amount of bisphenol A (pereent)/VC* 0.02 0.02 0.03 0.030.01 0.04 0.01 O. 01 Particle size distribution (percent):

60 mesh pass 97. 8 99. 5 96. 5 98. 0 97. 0 97. 0 99. Q .19. 8 100 meshpass. 40. 11 50. l 40. 8 47. 5 40. 3 40. 3 58.8 60. 1 200 mesh pass4.0 1. 8 3.9 '2. 0 3.5 3.5 3. 0 2. 0 D 0I absorption (pereent). 30.5 33.4 29. 5 32. 3 d0. 3 30. 3 40. 0 36.8 Fish eye (pieces 30 12 23 2O 13 130 25 Initial color 1 0 1 0 1 0 0 0 Thermal stability (min.) 100 100 10090 100 00 100 100 *(Percent)/VC means percent based on the weight of thevinyl chloride.

Examples 9-1 1 and Control 13 Experiments as described in Example 1 werecarried out, the only difference being that the cetyl alcohol wasreplaced by other saturated fatty alcohols. The results obtained aregiven in Table 3 below.

TAB LE 3 Experiment Control Number 9 1O 11 13 Octyl Decanoyl Myristyln-Butyl Kind of alcohol added alcohol alcohol aleo 01 alcohol Particlesize distribution (percent):

60 mesh pass 96. 0 98. 8 96. 8 80. 5 100 mesh pass. 50. 3 51.0 46. 560.3 200 mesh pass 4. 0 2. 5 3.0 12.1 D OI absorption (pereent) 35.6 30.1 31. 5 20. 3 Fish eye 25 30 250 Initial color l. 0 1 5 Thermalstability (n1in.) 90 100 100 80 The results set forth in Table 3 showthat when n-butyl a1- cohol was employed, there was no improvement inparticle size distribution and thermal stability. Moreover, the DOPabsorption and initial color values were deteriorated as compared-to thecorresponding values obtained in the absence of cetyl alcohol.

Example 12 and Control 14 Experiments as described in Example 1 wereconducted; the only difference being that sorbitan monooleate wasreplaced by either sorbitan trioleate or sorbitan monolaurate. Theresults obtained are given in Table 4 below.

The results set forth in Table 4 show that when sorbitan monolaurate wasemployed, the particle size distribution of PVC proved to beextraordinary. Additionally, there was no improvement in the initialcolor.

Examples 13 and 14 Experiments as described in Example 1 were conducted;the only difference being that biphenol A (the reducing agent) wasreplaced by 0.01 percent of hydroquinone or 0.01 percent of sulfoxylate(SFS prepared from a formaldehyde condensate. The results obtained aregiven in Table 5.

For the sake of comparison, 0.01 percent of ferrous sulfate or 0.01percent of oxalic acid (both well-known reducing agents) was employed.in the former case, PVC exhibited yellow coloration upon drying. In thelatter case it exhibited a pale red coloration upon drying.

Examples 15 and 16, and Control 15 Experiments as described in Example 1were carried out; the only difference being that biphenol A was addedduring the course of the polymerization. The results obtained are givenin the following Table 6.

TABLE 6 No. Control 15 Example 3 5 15 16 Time (hr) elapsed from thestart of polymerization to the point a! which the biphenol A was added 67.5 9 Rate of conversion when the biphenol A was added 41 55 73 Totalpolymerization time Suspended 1 1 10.3

(hr) after 15 hours Particle 60 mesh pass 75.9 98.5 99.0 size 45 dis-100 mesh pass 43.6 46.6 51.1

tribution 200 mesh pass 4.2 3.9 3.5 initial color 0 0 0 Thermalstability (min) 70 90 100 As is obvious from the results of Table 6above, in Examples 15 and 16, no particular retardation was observed inthe progress of the reaction, and the resultant products exhibitedsuperior properties. In contrast thereto, with Control 15 the progressof the polymerization reaction was remarkably delayed. The pressurewithin the polymerization vessel showed no reduction even 15 hours afterthe start of the reaction. The reaction was therefore suspended.Moreover at that time only a 70 percent rate of conversion and a verywide PVC particle size distribution showing a large amount of fineparticles was attained.

Examples 17 23, and Controls 16 22 Five-hundred liters of water, 200 gof partially saponifled polyvinyl acetate, 500 g of cetyl alcohol, 75 gof sorbitan mono-oleate and 250 kg of vinyl chloride monomer were placedinto a stainless steel polymerization vessel having an inner capacity of1,000 liters. The mixture was polymerized at 57 C in the presence of oneof the catalysts given in Table 7. Upon completion of thepolymerization, 50 g of bisphenol A dissolved in 2 liters of methanolwere added to the system. The system was stirred. The polymerizationproduct was then dehydrated and dried. PVC having the properties givenin the 75 following Table 7 was thereby obtained.

For the sake of comparison, experiments similar to the above werecarried out. In these comparative experiments, cetyl alcohol, sorbitanmonooleate, and the bisphenol .A added on completion of thepolymerization were not emsaid catalyst is selected from the groupconsisting of dialkylperoxy dicarbonate,azo-bis-Z,4-dimethylvaleronitrile, azobis-2,4,4-trimethylvaleronitrile,azo-bis-4-methoxy-2,4- dimethylvaleronitrile, acetylcyclohexyl sulfonylperoxide and ployed. The properties of the PVC thus prepared are setforth 5 mixtures thereof, the polymerization is conducted in the in thefollowing Table 7 in the columns designated as Controls presence of afatty alcohol having from eight to 18 carbon 16 22. atoms and sorbitanoleate, and an organic reducing agent TABLE 7 Example Number 17 18 20 2122 23 DMVN DMVN DMVN (0.015) (0.015) (0.015) Kind of catalyst and amountof catalyst ()ll lill illl liCl 'IMVN MOVN ACSP (pereen l)/V I (0.015)(0.015) (0.02) (0.025) (0.015) (0.015) (0.015)

Total polymerization time (llr.) 10. 5 10.0 11.0 11.0 0.0 8. 5 0. 5l'urtiele size distribution (percent):

00 mesh puss 0!). l 00. 8 08.8 00.0 00. 1 08.0 98.0 '15. 5 50. ii 40. 044. 5 46. 0 40.1 50. 0 200 mesh I) 2.5 0 4.0 3.5 l)()l uhsorpl )ll(percent), 20.0 30. 0 31.1 30. 5 Fish eye (pieces I 40 35 35 20 Initialcolon. 0 1 1 l 'lherrnul stuillllty (mln.) 100 100 100 00 ControlNumber". m I 11 18 '1 21 22 DMVN DMVN DMVN (0. 015) (0.015) (0.015) Kindof catalyst and amount of catalyst OPP BPP HPP BOP 'IMVN MOVN ACS I(percent) /V C" (0.015) (0.015) (0.02) (0.025) (0.015) (0.015) (0.015)

Total polymerization time (hr.) 10.5 10.0 11.0 11.0 0. 0 8. 5 0. 5Particle size distribution (percent):

60 mesh pass 77. 7 70. 6 66. 9 60. 8 80. 3 86. 9 60. 0 100 mesh pass.39. 8 37. 8 40. 8 31. 2 35. 5 40. 1 30. 8 200 mesh pass 2. 5 5. 0 2.0 4.3 2. 5 3.0 2. 1 DOP absorption (percent) 18.0 18.8 15.9 16.0 19.5 20.315. 0 Fish eye (pieces) 100 107 135 233 300 201 193 Initial color 3 4 44 4 4 5 'llwrnml stability (min.) .10 80 80 00 8O 00 70 l'm'cvnU/Vinlunns purcent lmsml on tho weight of the vinyl chloride.

ll 1' l': l)i-svv-lmiyl lmroxy (ilrurhonnte;

llll': llli-yli-olumy mroxy divnrinnmln;

Examples 24 26 and Controls 23 25 5 Five-hundred liters of water, 125 gof partially saponified polyvinyl acetate (saponification degree: 80mole percent; average degree of polymerization: 1,820), 75 g of methylcellulose (viscosity of 2 percent aqueous solution at 20 C: 45 cps),cetyl alcohol and sorbitan monooleate each in the amount given in Table8, 225 kg of vinyl chloride and 25 kg of vinyl acetate, were chargedinto a stainless steel polymerization vessel having an inner capacity of1,000 liters. The mixture was copolymerized at 58 C in the presence of62.5 g of DMVN as a catalyst. Fifty gram of bisphenol A and 25 g ofhydroquinone were dissolved in 3 liters of methanol. This methanolsolution was added to the polymerization system 1 1 hours after thestart of the polymerization. The polymerization was then continued foran additional hour. The results obtained are given in the followingTable 8.

TABLE 8 Example Control Number 24 25 26 23 24 25 Amount of cetyl alcohol(percent) C 0.1 0.3 0.1 0 0.3 0 Amount of sorbitan monooleate(percent)/VC 0.05 0.05 0 1 0 O 0 05 Particle size distribution(percent):

60 mesh pass 99.9 99.8 100.0 90.1 91.1 95.6 100 mesh pass 47. 6 43. 039. 9 51. 1 49. 8 53.3 200 mesh pass 4.3 3.0 2.0 5. 6 5.0 6. 0 DOPabsorption (percent).-.. 25.6 23.0 28.8 10.1 0.0 12.3 Initial color- 0 04 3 4 Thermal stability (min.) 80 90 8O 50 50 40 *(PercenQ/VC meanspercent based on the weight of the vinyl chloride.

What is claimed is:

1. in a method for suspension polymerizing vinyl chloride monomer or amixture of vinyl monomers containing vinyl chloride as its maincomponent in an aqueous reaction medium containing a suspending agentand in the presence of a polymerization catalyst, the improvement whichcomprises selected from the group consisting of bisphenol A, hydroquinone, sulfoxylate of the condensate of formaldehyde, and mixturesthereof is added to the reaction medium when a rate of conversion of atleast 50 percent is realized.

2. The method of claim 1, in which the catalyst is selected from thegroup consisting of di-isobutyl peroxy dicarbonate, di-isopropyl peroxydicarbonate, di-2-ethyl-hexylperoxy dicarbonate, di-cyclohexyl-peroxydicarbonate, bis-1,4-tertiary-butyl cyclohexyl peroxy dicarbonate,azo-bis-2,4-dimethylvaleronitrile, azo-bis-2,4,4-trimethylvaleronitrile, azo-bis-4- methoxy-Z,4-dimethylvaleronitrile andacetylcyclohexysulfo nyl peroxide, and the catalyst is present in anamount of at most 0.2 percent by weight, based on the weight of thevinyl chloride or mixture of vinyl monomers containing vinyl chloride.

3. The method of claim 1 in which the fatty alcohol is selected from thegroup consisting of octyl alcohol, decanoyl alcohol, lauryl alcohol,myristyl alcohol, cetyl alcohol and stearyl alcohol and the fattyalcohol is present in an amount of from 0.03 to 0.1 percent by weight,based on the weight of the vinyl chloride or mixture of vinyl monomerscontaining vinyl chloride.

4. The method of claim 1 in which the sorbitan oleate is selected fromthe group consisting of sorbitan monooleate, sorbitan trioleate andsorbitan sesquioleate, and the sorbitan oleate is present in an amountof from 0.01 to 0.5 percent by weight based on the weight of the vinylchloride or mixture of vinyl monomers containing vinyl chloride.

5. The method of claim 1 in which the organic reducing agent is added inan amount of from 0.005 to 0.5 percent by weight based on the weight ofthe vinyl chloride or mixture of vinyl monomers containing vinylchloride.

6. The method of claim 1 in which the organic reducing agent is added tothe reaction medium on completion of the polymerization of the vinylchloride or the mixture of vinyl monomers containing vinyl chloride.

TJNTTTn STATES PATENT oTTTcT I QER'HWQATE @E CURRTEQTWN Patent No.3,671,508 Dated June 20,, 1972 Inventor(s) Shunichi Koyanagi ,et. a1.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below-z In thegrant only, insert columns 3 and 4, as shown on the attached sheet, 7

Signed and sealed this 26th day of December 1972.

(SEAL) Attest:

EDWARD M.FLETCHER ,JR. ROBERT GOT'ISCHALK Attesting Officer 7Commissioner of Patents USCOMM-DC 60376-P69 w u 5. GOVERNMENT PRINTINGOFFICE: I969 0-366-334.

F ORM PO-l 050 (10-69) Inventor Shunichi Koyanagi June 20, 1972 Datedamount of the vinyl chloride monomer or mixture of vinyl monomerscontaining vinyl chloride monomer. if it is added in an amount of lessthan 0.03 percent. the alcohol will not exert a sufficient effect. Theaddition of more than 0.1 percent alcohol is uncalled for as suchaddition will not afford a proportional increase in its desired effect.The sorbitan oleate used with the higher fatty alcohol is exemplified bysorbitan monooleate, sorbitan trioleate and sorbitan sesquioleate. Thesorbitan oleate is preferably used in an amount of from 0.0] to 0.5percent by weight, based on the weight of the vinyl chloride monomer ormixture of vinyl monomers containing vinyl chloride monomer. if it isused in a amount of less than 0.01 percent by weight, the sorbitanoleate will not have a sufficient effect. if it is used in an amountover 0.5 percent, the rate of reaction will be substantially decreased.The reducing agent, which is added to the polymerization system when therate of conversion reaches at least 50 percent, is selected from thegroup consisting of hydroquinone, biphenol A, and sulfoxide preparedfrom a formaldehyde condensate. The reducing agent may be added to thesuspension after the polymerization is over providing that the rate ofconversion of the system is at least 50 percent. The reducing agent isadded to the polymerization system in an amount of at least 0.005percent by weight, based on the amount of vinyl chloride polymer.Preferably it is added in an amount of from 0.005 to 0.05 percent, basedon the amount of vinyl chloride polymer because. if it is added in anamount more than 0.05 percent, the thermal stability ofthe vinylchloride polymer produced may be adversely affected.

it should be noted that with respect to each of the catalyst, suspendingagent. fatty alcohol, sorbitan oleate and reducing agent, one can employone representative compound or a mixture of representative compoundsfrom the above given respective groups. Various organic solvents mayalso be used to control the molecular weight of the polyvinyl chloride.

The polymerization of the present invention is preferably carried out ata temperature of from 30 to 70 C, which temperature range is that whichis usually employed in the known methods for the suspensionpolymerization of vinyl chloride. The method of the present inventioncan however be effectively carried out even at temperatures below 30 C.In such case. a special catalyst such as trialkyl boron or an alcoholsuch as methanol or ethanol may be concurrently employed.

The method of the present invention is applicable not only to thepolymerization of vinyl chloride alone, but also to the copolymerizationof vinyl chloride with other vinyl monomers copolymerizable with it.Examples of such vinyl monomers include vinyl esters, vinyl ethers.alkyl acrylates, alkyl methacrylate, maleic anhydride, alkyl esters ofmaleic acid or of fumaric acids. alkyl itaconates, aromatic vinyls,vinylidene halides, vinyl halides excepting vinyl chloride, andtx-olefins having at placed in a tube, the bottom ofwhich was filledwith glass fiber to permit removal of DOP. The tube was then placed in acentrifugal separator and was rotated therein at a speed of 3,000 rpm,for a period of l hour. The separated DOP was removed, and the PVC whichhad absorbed DOP was weighed. The ratio (in percent) of DOP absorbed by100 g of PVC was derived from the ratio of the weight of PVC before ithas absorbed DOP to that of PVC after it had absorbed DOP.

2. Initial Color 10 Fifty parts of DOP, l part of dibutyltin dilaurateand 0.5 part of cadmium stearate were added to I pans of the polyvinylchloride (PVC) and mixed therewith at 100 C, for 30 minutes. The mixturewas then molded into a X mm angular stick by means of an extruder havingan inside diameter of mm. The cylinder temperature of the extruder was160 C. The die temperature was 195 C. The color of the stick as observedwith the naked eye was used as a measure of the initial color ofthe PVC.

3. Thermal Stability 2.5 parts of dibutyltin maleate and 0.5 part ofstearic acid were added to 100 parts of PVC. The mixture was kneaded for10 minutes on a hot roll at l70 C to produce a 0.7 mm thick sheet. Thesheet was heated at l85 C in a gear oven. The time elapsed before thesheet blackened was used as a measure of the thermal stability of thePVC.

4. Fish Eye Fifty parts of DOP, 2.0 parts of dibutyltin dilaurate, 0.8part of cetyl alcohol. 0.1 part of barium stearate, 0.1 part of cadmiumstearate, 0.5 part of titanium oxide, and 0.l part of carbon black wereadded to 100 parts of PVC. The mixture was kneaded for 7 minutes on ahot roll at l50 C to produce a 0.2 mm thick sheet. Light was passedthrough the sheet and the number of fish eyes per 100 cm of the sheet,as observed with the naked eye, was employed as an indication of theextent of fish eye production in the PVC.

Controls l ll Five-hundred liters of water were placed into a stainlesssteel polymerizing vessel, having an inner capacity of L000 liters.Two-hundred gram of partially saponified polyvinyl acetate(saponification degree: 8i mole percent, average degree ofpolymerization: 1,820), cetyl alcohol and sorbitan monooleate each inthe amount given in Table l, and 250 kg of vinyl chloride monomer weredissolved therein. Upon the further addition of 37.5 g of lPP,polymerization was carried out at 57 C for 10 hours. Unreacted vinylchloride monomer was removed from the system. The polymerization productwas stirred for 15 minutes with (or without) an addition of a methanolsolution of biphenol A in the amount given in Table l. Then thepolymerization product produced was dehydrated and dried. The propertiesof the PVC thus produced are shown in the following Table l.

TAB LE 1 Control Number 1 2 3 4 5 6 i 8 J 10 11 12 Amount of cetylalcohol (percent)/\'C' 0 0.01 0. Z 1. 5 U 0 0 0 0. 2 0. 2 0 0.2 Amountof sorbitan inonooleate (percenU/VC 0 0 0 0 0.003 0. 05 1.0 0 0. 05 0.05 0.05 Amount of bisphenol A (porccnt) \'C' l) l) 0 O 0 0 0 0.02 0 0.02 0.02 0. 1 Particle size distribution (percent):

mesh pass 88.5 39. 2 00.3 88.3 01.5 92. 0 43. 5 88.5 J7. 8 0.3 92. 0 97.8

mesh pass.. 38.3 40.5 -13. 5 35.5 45. 3 50.1 21.0 38.3 49.9 43. 5 50.1-19. 9

200 mesh pass 3.6 2.9 4.5 4,0 5. 0 5.9 2. 3 3. 6 4. 0 4. 5 5. 0 4.0 D01absorption (percent) 17. 5 16. 3 16. 5 15. 9 17.8 28. 0 17. 5 30. 5 16.5 28. J 30. 5 Fish eye (pieces) 1 120 M0 200 1'10 43 110 43 30 Initialcolor -t 4 4 3 4 4 4 3 Ll 3 1 'lliorlnalstnhility(niin.) 80 90 J0 90 80'80 80 90 S0 80 60 '(I'vi'cvnU/VC 1llt:1llS percent bnsud on the weightof the vinyl chloride.

most four carbon atoms.

The method of the present invention will now be further described withreference to the following examples wherein the propenies of thepolyvinyl chloride produced were deter mined by the following testmethods.

I. Plasticizer Absorption To polyvinyl chloride (PVC) was added twiceits amount of di'Z-ethyI hexylphthalate (DOP). The resultant mixture waspermitted to stand at room temperature for l hour. it was then Examplesl-8 Five-hundred liters of water, 200 grams of partially saponifiedpolyvinyl acetate (saponification degree: 81 mole percent; averagedegree of polymerization: 1.820), cetyl alcohol and sorbitan monooleateeach in the amount given in Table 2, and 250 kg of vinyl chloridemonomer were charged into a stainless steel polymerization vessel havingan inner capacity of L000 liters. 37.5 g of lPP were added thereto and75 polymerization was carried out at 57 C for l0 hours. Un-

2. The method of claim 1 in which the catalyst is selected from thegroup consisting of di-isobutyl peroxy dicarbonate, di-isopropyl peroxydicarbonate, di-2-ethyl-hexylperoxy dicarbonate, di-cyclohexyl-peroxydicarbonate, bis-1,4-tertiary-butyl cyclohexyl peroxy dicarbonate,azo-bis-2,4-dimethylvaleronitrile, azo-bis-2,4,4-trimethylvaleronitrile, azo-bis-4-methoxy-2,4-dimethylvaleronitrile andacetylcyclohexysulfonyl peroxide, and the catalyst is present in anamount of at most 0.2 percent by weight, based on the weight of thevinyl chloride or mixture of vinyl monomers containing vinyl chloride.3. The method of claim 1 in which the fatty alcohol is selected from thegroup consisting of octyl alcohol, decanoyl alcohol, lauryl alcohol,myristyl alcohol, cetyl alcohol and stearyl alcohol and the fattyalcohol is present in an amount of from 0.03 to 0.1 percent by weight,based on the weight of the vinyl chloride or mixture of vinyl monomerscontaining vinyl chloride.
 4. The method of claim 1 in which thesorbitan oleate is selected from the group consisting of sorbitanmonooleate, sorbitan trioleate and sorbitan sesquioleate, and thesorbitan oleate is present in an amount of from 0.01 to 0.5 percent byweight based on the weight of the vinyl chloride or mixture of vinylmonomers containing vinyl chloride.
 5. The method of claim 1 in whichthe organic reducing agent is added in an amount of from 0.005 to 0.5percent by weight based on the weight of the vinyl chloride or mixtureof vinyl monomers containing vinyl chloride.
 6. The method of claim 1 inwhich the organic reducing agent is added to the reaction medium oncompletion of the polymerization of the vinyl chloride or the mixture ofvinyl monomers containing vinyl chloride.